Avena fatua and A. ludoviciana (commonly known as wild oats) are the most problematic winter grass species in fallows and winter crops in the northeast region of Australia. A series of experiments were conducted to evaluate the performance of glyphosate and alternative post-emergence herbicides on A. fatua and A. ludoviciana. This study reports the world’s first glyphosate-resistant (GR) biotypes of A. fatua and A. ludoviciana. The glyphosate dose required to kill 50% of the plants (LD50) and to reduce 50% of the biomass (GR50) for the GR biotype of A. fatua was 556 g a.e./ha and 351 g a.e./ha, respectively. These values for A. ludoviciana were 848 g a.e./ha and 289 g a.e./ha. Regardless of the growth stage (3-4 or 6-7 leaf stages), clethodim (120 g a.i./ha), haloxyfop (78 g a.i./ha), pinoxaden (20 g a.i./ha), and propaquizafop (30 g a.i./ha) were the best alternative herbicide options for the control of A. fatua and A. ludoviciana. The efficacy of butroxydim (45 g a.i./ha), clodinafop (120 g a.i./ha), imazamox + imazapyr (36 g a.i./ha), and paraquat (600 g a.i./ha) reduced at the advanced growth stage. Glufosinate (750 g a.i./ha), flamprop (225 g a.i./ha), and pyroxsulam + halauxifen (20 g a.i./ha) did not provide effective control of Avena species. This study identified alternative herbicide options to manage GR biotypes of A. fatua and A. ludoviciana.